Applications are changing and so is the infrastructure required to support these applications. Earlier, as applications were developed and deployed as monoliths, so was the network infrastructure around it. A monolith needed services from the perimeter proxy like security and monitoring. But as the monolithic application gets broken up into several smaller parts, the infrastructure to support it has to change.
At the center of this change is how the proxy has adapted to providing infrastructure for services which are smaller pieces of the monolithic application. The culmination of services has also created a service mesh pattern where typical application functions that were baked into an application (like traceability library integrated with application) have moved to the proxy.